package com.icehand.wechat.utils;

import lombok.extern.slf4j.Slf4j;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.springframework.util.Base64Utils;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.spec.InvalidParameterSpecException;
import java.util.Arrays;
import java.util.Base64;

@Slf4j
public class AESUtil {
	static {
		//BouncyCastle是一个开源的加解密解决方案，主页在http://www.bouncycastle.org/
		Security.addProvider(new BouncyCastleProvider());
	}

	public static String decrypt(String data, String key, String iv, String encodingFormat) throws Exception {
		 byte[] dataByte = Base64.getDecoder().decode(data);
		 byte[] keyByte = Base64.getDecoder().decode(key);
		 byte[] ivByte = Base64.getDecoder().decode(iv);
		 try {
		 	Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
		 	SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
		 	AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
		 	parameters.init(new IvParameterSpec(ivByte));
		 	cipher.init(Cipher.DECRYPT_MODE, spec, parameters);
		 	byte[] resultByte = cipher.doFinal(dataByte);
		 	if (null != resultByte && resultByte.length > 0) {
			    return new String(resultByte, encodingFormat);
		 	}
		 	return null;
		 } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidParameterSpecException | InvalidKeyException | InvalidAlgorithmParameterException | IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException e) {
		 	e.printStackTrace();
		 }
		return null;
	}

	public static String decrypt(String encryptedData, String sessionKey, String iv) {
		String result = null;
		// 被加密的数据
		byte[] dataByte = Base64Utils.decode(encryptedData.getBytes(Charset.forName("utf-8")));
		// 加密秘钥
		byte[] keyByte = Base64Utils.decode(sessionKey.getBytes(Charset.forName("utf-8")));
		// 偏移量
		byte[] ivByte = Base64Utils.decode(iv.getBytes(Charset.forName("utf-8")));
		try {
			// 如果密钥不足16位，那么就补足. 这个if 中的内容很重要
			int base = 16;
			if (keyByte.length % base != 0) {
				int groups = keyByte.length / base
						+ (keyByte.length % base != 0 ? 1 : 0);
				byte[] temp = new byte[groups * base];
				Arrays.fill(temp, (byte) 0);
				System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
				keyByte = temp;
			}
			// 初始化
			Security.addProvider(new BouncyCastleProvider());
			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding", "BC");
			SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
			AlgorithmParameters parameters = AlgorithmParameters
					.getInstance("AES");
			parameters.init(new IvParameterSpec(ivByte));
			cipher.init(Cipher.DECRYPT_MODE, spec, parameters);// 初始化
			byte[] resultByte = cipher.doFinal(dataByte);
			if (null != resultByte && resultByte.length > 0) {
				result = new String(resultByte, StandardCharsets.UTF_8);
			}
		} catch (NoSuchAlgorithmException | NoSuchPaddingException
				| InvalidParameterSpecException | IllegalBlockSizeException
				| BadPaddingException | InvalidAlgorithmParameterException | InvalidKeyException
				| NoSuchProviderException e) {
			log.error(e.getMessage(), e);
		}

		return result;
	}
}